As is known, the use of seat belts is compulsory under many highway codes, and the vehicles that circulate in countries where their use is compulsory are fitted with an acoustic signalling device to indicate that the occupants have not fastened their seat belts. Said device generally consists of a buzzer that is activated when the vehicle exceeds a given minimum speed. The acoustic signal is usually accompanied by an optical signal to indicate that the seat belts have not been fastened which consists of a specific warning light on the vehicle's instrument panel.
To induce the occupants of vehicles to fasten seat belts various systems have been proposed which automatically deactivate the vehicle's on-board devices and prevent these from functioning until the seat belts are fastened. For example a system has been proposed that automatically prevents the vehicle's air conditioning system from working, while Japanese patent application JP2004136888 proposes a system that automatically prevents the vehicle radio from working and activates an acoustic signalling device that transmits, at an increasingly high volume, a recorded voice message inviting the occupants to fasten their seat belts.
However the Applicant has noted that the use of such automatic systems to prevent on-board systems from functioning may result in the occupants of the vehicle erroneously perceiving the presence of an on-board system malfunction, which could subsequently damage the image of the vehicle manufacturer.